I like the concept.  I found the controls difficult - I guess backwards from what i expected.  It makes sense, sense i am controlling the curtain, and not the vampire.  But it wasn't very intuitive.  it would also be nice if there was a way to restart after losing, without refreshing the whole page.  

My biggest issue was with the audio.  when the sun hits the vampire, it cascaded the hurt sound which was overwhelming.   I had to mute my computer.  maybe consider adding a delay between each play of the sound?

There seems to be a bug where the game freezes when the curtain touches the vampire!